Explosive type severing device for cables, rods and the like

ABSTRACT

A severing device is disclosed for severing an element such as a cable, rod, bolt or the like using pure shear forces produced by gas pressure resulting the firing of a explosive charge having an energy per unit mass of more than 1000 joules/gram and a detonation speed of over 3000 ms. The device includes a cylindrical enclosure which defines a housing for the explosive charge at one end thereof and a chamber which is in communication with said housing and itself houses a piston which is movable responsive to the firing of the charge. The piston includes a knife end which bears against the element to be severed and is in the form of a dihedral defined by a first plane parallel to the longitudinal axis of the chamber and a second plane which is inclined relative to that axis.

United States Patent Lagofun July 22, 1975 [54] EXPLOSIVE TYPE SEVERING DEVICE FOR 3,452,631 7/1969 Brizzolara 83/639 X CABLES RODS AND THE LIKE 3,523,477 8/1970 Miller 83/639 3,707,896 1/1973 Kononenko et al. 83/639 or: Guy Jean La ofun, Tarbes, France 3,739,673 6/1973 Temple 83/639 [73] Assignee: Etat Francais, Paris, France Primary ExaminerFrank T. Yost [22] Flled? 1974 Attorney, Agent, or FirmLarson, Taylor & Hinds [21] Appl. No.: 433,301

Related US. Application Data [57] ABSTRACT [63] Continuatiomimpart of 358 407 May 8 A severing device is disclosed for severing an element 1973, Pat 3,873,786 such as a cable, rod, bolt or the like using pure shear forces produced by gas pressure resulting the firing of [30] Foreign Application priority Data a explosive charge having an energy per unit mass of Jan 11 1973 France 73 00809 more than 1000 joules/gram and a detonation speed of over 3000 ms. The device includes a cylindrical enclo- [52] U S Cl 83/580 83/639, 114/221 A sure which defines a housing for the explosive charge [51] Int Cl 3 B26D 5/12 at one end thereof and a chamber which is in commu- [58] i earch 83/639 114/221 A nication with said housing and itself houses a piston which is movable responsive to the firing of the charge. The piston includes a knife end which bears [56] References cued against the element to be severed and is in the form of UNITED STATES PATENTS a dihedral defined by a first plane parallel to the longi- Osgood tudina] axis of the chamber and a econd plane 2,495,953 1/1950 Austin 83/639 X is inclined relative to that axis 2,970,506 2/l96l Temple et al 83/639 3,246,396 4/1966 Temple et al 83/639 X 10 Claims, 1 Drawing Figure PIOb I6 2 25 l4 9 e 2. 28 Z 260 4\ 3O 30 q x C L\\ l2 I2 PATENTED JUL 2 2 I975 EXPLOSIVE TYPE SEVERING DEVICE FOR CABLES, RODS AND THE LIKE CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of US. ap plication Ser. No. 358,407, filed on May 8, 1973, now U.S. Pat. No. 3,873,786.

FIELD OF THE INVENTION The present invention relates to a device for severing rods, bolts, cables and the like using sheer forces generated by an exploding charge.

BACKGROUND OF THE INVENTION In my copending application Ser. No. 358,407, filed on May 8, l973, now US. Pat. No. 3,873,786, there is described a severing or shearing apparatus whereby an element or part to be severed is subjected to pure shear stresses caused by a sudden increase in gas pressure resulting the explosion of an explosive charge having a useful energy per unit mass of over 1000 joules/gram (j/g), and preferably between 2000 and 5000 j/g, and a rate of detonation or detonation speed of over 3000 ms., and preferably between 7000 and 8000 ms. The explosive charge is arranged or housed in an enclosure or recess which opens onto a surface delimited by a movable part or member which bears directly or indirectly on the element to be severed, so that the initial volume of the gas from the explosion is at most equal to the volume swept by the delimited surface of the mobile part adjacent the charge housing during the useful movement of the severed portion of the element. Reference is made to the above-identified application Ser. No. 358,407, now US. Pat. No. 3,873,786, for a further description of the method and apparatus in question and the content of that Patent is hereby incorporated by reference.

Although the severing device set forth in the application referred to is of broad applicability, the specific devices disclosed therein are concerned with electrical switches and circuit breakers. The present invention specifically concerns a device for severing or sectioning cables, bolts, rods and the like and thus falls in the class of devices generally termed rod cutters or cable cutters.

In accordance with the present invention, a device for sectioning or severing an element such as cable, rod or the like by pure shear forces generated by substantially instantaneous establishment of a gas pressure resulting from the firing of an explosive charge with a useful energy per unit mass of more than 1000 joules/- gram and a detonation speed of over 3000 ms., the charge being located in an enclosure or housing which opens on a delimited surface of a movable part located within said housing so that the initial volume of the gases from the explosion is at most equal to the volume swept by the delimited surface during the useful displacement of section portion of the element to be severed, the device being characterized in that the movable part comprises a piston located within a cylinder and including a knife edge at one end thereof which engages the element to be severed. The knife edge cooperates with a correspondingly shaped stationary knife to form the blades of a pair of shears. The two knives are preferably of a dihedral shape defined by a first plane parallel to the longitudinal axis of the cylinder and second plane inclined relative to that axis. Further, a notch is advantageously provided in the dihedral faces to provide close contact with the element to be severed. An adjustable plug located in an open end of the cylinder supports the stationary knife and provides variation of the position thereof relative to the movable knife.

Other features and advantages of the invention will be set forth in, or apparent from, the detailed description of a preferred embodiment found hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS The single FIGURE in the drawings is a longitudinal section of a severing or sectioning device in accordance with a preferred embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the single FIGURE in the drawings, an exemplary embodiment of the cutting or sectioning device of the invention is shown. The device includes a generally cylindrical housing 10 which includes a threaded open end 10a and a closed end 10b. A pair of aligned, diametrically opposed openings 12 permit the passage of a rod, cable or the like, denoted C, through the housing 10, as illustrated, so that cutting of the cable C can be effected. A charge housing or recess 14 formed at the closed end 10b of cylindrical housing 10, houses the wire carrying block 16 of a conventional exposed wire detonator or detonation initiator. An opening 18 in closed housing end 10b permits passage of electrical connections 20 into housing 10, these connections 20 being insulated from housing 10 by an insulating plug 22 which is received in opening 18. An explosive charge 24 is housed within charge housing 14. The charge 24, which is preferably made up of lead nitride and pentrite is located within ring or annulus 25 located within charge housing 14, is in contact with the detonating wires of wire-carrying block 16 and is adapted to be detonated responsive to a control signal transmitted over wires or connectors 20 from a remote control unit (not shown).

A piston 26 is slidingly mounted within cylindrical housing 10. Piston 26 includes first and second circumferential grooves 26a spaced along the length thereof in which are received first and second fluid-tight packing joints or O-rings 28. The end of piston 26 opposite charge housing 14 terminates in a knife or cutting portion 30. The knife 30 is defined by two planes, one parallel to the longitudinal axis of cylinder 10 and a second which is inclined with respect to this axis to form a clearance angle. This configuration aids in avoiding jamming of the piston 26 with the end of the cable C after completion of the sectioning operation. Knife 30 includes a notch 30a in the dihedral face between the two planes referred to above allowing the knife edge 30 to fit more closely to the cable or rod C to be sectioned and to aid in orienting the edge of the knife 30 so as to be perpendicular to the axis of the cable or rod.

A second, stationary knife 32 of a shape similar to that of knife 30 and including a corresponding notch 32a in the dihedral face thereof, forms the second blade of a pair of shears constituted by knives 30 and 32. A plug 34 is threadably received in the threaded end 10a of cylinder 10 and is screwed into cylinder 10 an appropriate distance so as to bring knife 32 into proper relationship with respect to knife 30.

In operation, change 24 explodes responsive to a firing signal transmitted to detonation initiator block 16 and the resultant pressure created acts on piston 26 to provide longitudinal displacement thereof. The knife end 30 of piston 26 thus causes shearing of cable or rod C. The energy released by the explosion of charge is converted into the kinetic energy of the piston 26 and the relatively limited shearing work performed. and is absorbed in the impact of knives 30 and 32. During actual testing operations, a 4-mm diameter steel cable was severed in less than 300 microseconds using a charge of mg. of lead nitride and 20 mg. of pentrite. Various tests performed under these conditions have indicated an actual operating time between the firing order (signal) and the shearing of the cable of less than several microseconds.

Although the invention has been described relative to an exemplary embodiment thereof, it will be understood by those skilled in the art that variations and modifications may be effected in this embodiment without departing from the scope and spirit of the invention.

I claim:

1. A device for severing an element such as cable, rod or the like using shear forces generated by gas pressures resulting from the explosion of explosive charge having a useful energy per unit mass of greater than 1000 joules per gram and a detonation speed of greater than 3000 ms., said device comprising a housing defining a recess in which said charge is housed and which opens on a surface delimited by a movable piston that engages the element to be severed, the initial volume presented to the explosion gases, defined by the explosive charge and the recess in which said charge is housed, being no greater than the volume swept by the gas during the useful movement of the severed portion of the element to be severed, said movable piston being located within a chamber and being movable longitudinally therein, and said piston including a knife end which, in the rest position of the piston prior to the severing operation, contacts and bears against the element to be severed.

2. A device as claimed in claim 1 wherein said chamber is defined by a cylindrical enclosure and is in communication with said charge housing.

3. A device as claimed in claim 2 wherein said charge housing further comprises initiator means located therein for detonating said charge.

4. A device as claimed in claim 3 wherein said explosive charge is located within a ring situated within said charge housing.

5. A device as claimed in claim 1 wherein said knife end of said piston comprises a dihedral defined by a first plane parallel to the longitudinal axis of said chamber and a second plane which is inclined at an angle relative to said axis.

6. A device as claimed in claim 5 wherein said knife end of said piston includes a notch in the middle of the dihedral face for facilatating close contact between the knife edge and the element to be severed.

7. A device as claimed in claim 6 further comprising a stationary knife located within said chamber and of a shape corresponding to said knife end of said piston.

8. A device as claimed in claim 1 further comprising a stationary knife located within said chamber which, in cooperation with said knife end of said piston, constitute the blades of a pair of shears.

9. A device as claimed in claim 8 further comprising a plug member extending to said chamber for supporting said stationary knife.

10. A device as claimed in claim 9 wherein said plug member is threadably received in said chamber so as to permit adjustment of the amount said plug member extends into said chamber. 

1. A device for severing an element such as cable, rod or the like using shear forces generated by gas pressures resulting from the explosion of explosive charge having a useful energy per unit mass of greater than 1000 joules per gram and a detonation speed of greater than 3000 ms., said device comprising a housing defining a recess in which said charge is housed and which opens on a surface delimited by a movable piston that engages the element to be severed, the initial volume presented to the explosion gases, defined by the explosive charge and the recess in which said charge is housed, being no greater than the volume swept by the gas during the useful movement of the severed portion of the element to be severed, said movable piston being located within a chamber and being movable longitudinally therein, and said piston including a knife end which, in the rest position of the piston prior to the severing operation, contacts and bears against the element to be severed.
 2. A device as claimed in claim 1 wherein said chamber is defined by a cylindrical enclosure and is in communication with said charge housing.
 3. A device as claimed in claim 2 wherein said charge housing further comprises initiator means located therein for detonating said charge.
 4. A device as claimed in claim 3 wherein said explosive charge is located within a ring situated within said charge housing.
 5. A device as claimed in claim 1 wherein said knife end of said piston comprises a dihedral defined by a first plane parallel to the longitudinal axis of said chamber and a second plane which is inclined at an angle relative to said axis.
 6. A device as claimed in claim 5 wherein said knife end of said piston includes a notch in the middle of the dihedral face for facilatating close contact between the knife edge and the element to be severed.
 7. A device as claimed in claim 6 further comprising a stationary knife located within said chamber and of a shape corresponding to said knife end of said piston.
 8. A device as claimed in claim 1 further comprising a stationary knife located within said chamber which, in cooperation with said knife end of said piston, constitute the blades of a pair of shears.
 9. A device as claimed in claim 8 further comprising a plug member extending to said chamber for supporting said stationary knife.
 10. A device as claimed in claim 9 wherein said plug member is threadably received in said chamber so as to permit adjustment of the amount said plug member extends into said chamber. 